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Subject: Re: Verified Null-Move Pruning, ICGA 25(3)

Author: Uri Blass

Date: 12:55:04 11/27/02

Go up one level in this thread


On November 27, 2002 at 15:15:50, Robert Hyatt wrote:

>On November 27, 2002 at 13:48:50, Frank Phillips wrote:
>
>>On November 26, 2002 at 20:02:06, Robert Hyatt wrote:
>>
>>>On November 26, 2002 at 16:21:00, Omid David Tabibi wrote:
>>>
>>>>On November 26, 2002 at 15:58:06, Gian-Carlo Pascutto wrote:
>>>>
>>>>>On November 26, 2002 at 15:55:56, Omid David Tabibi wrote:
>>>>>
>>>>>>So it is reasonable that on every program starting from a certain depth >adaptive null-move pruning will always construct a smaller search tree.
>>>>>
>>>>>Don't you mean the other way around?
>>>>>
>>>>
>>>>Yes :-)
>>>>
>>>>Starting from a certain depth, verified null-move pruning will always construct
>>>>a smaller search tree than the adaptive one.
>>>>
>>>>
>>>>
>>>>>--
>>>>>GCP
>>>
>>>
>>> I am doing some testing now.  First thing I noticed is that for WAC, the
>>>time-squared
>>>measurement went down very significantly for your algorithm.  And I have not
>>>modified
>>>anything such as turning null-move off when low material happens, since your
>>>idea will
>>>catch the zug problems.
>>
>>Have you tried Fine70?
>>
>>Frank
>
>Yes...  and I told Omid that this is a strange case as if I allow null-move in
>pawn-only
>endings, which turns it on for fine 70 of course, things get wrecked inside the
>search
>somehow.  A 45 ply search fails to see that Kb1 wins where normally an 18-19 ply
>search is enough...

No surprise

The idea is productive for detecting cases when there is one zugzwang but not
for cases when there is more than one zugzwang.

It is a bad idea to use it for pawn endgame.
If you want to use it to be theoretically sound(to see everything after enough
plies) then you need always to do verification search and not only in cases that
verify=true.

It may be possible to do verification search to reduced depth when
verify=false(for example by depth-=3; instead of depth--;)
if you want to protect yourself against the danger of zugzwangs in the middle
game and only if you detect a zugzwang to search again to bigger depth.

Uri



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